Preparation Of N-Type Polymers With Naphthalene Diimide For All-Polymer Solar Cell Applications

In recent years,n-type polymer acceptor materials have been widely studied in the field of organic optoelectronic devices,especially in the field of polymer solar cells.The nanphthalene diimide?NDI?-based polymers acceptor matierials which have high mobility of charge and the electron affinity have been reported in large numbers.Compared to fullerene derivative acceptor material,NDI-based n-type polymer acceptors exhibit better thermo/mechanical properties,light absorption and durability of the devices.In the all-polymer solar cell,looking for matching to the receptor material is a research focus.First of all,in order to find superior performance n-type receptor materials,we designed and synthesized a series of?Di-A?x-?D₂-A?_1-x random polymers with an electron-deficient unit and two electron-rich units.By controlling the two "D" unit content ratio,we designed and synthesized a series of polymer acceptor materials to find the best content ratio.Compared with the traditional D-A polymer receptor,there are a number of advantages,such as the complementarity between different "D" units,which can broaden the absorption range of visible light,and this random type polymer can adjust the aggregated structure in the film state.At the same time,we are looking for a suitable donor to match a series of synthetic acceptors.In order to explore the synthesis and photoelectric properties of this?D₁-A?_x-?D₂-A?_1-x random type polymer acceptor material,this paper attempts to do the following:1.Five?D₁-A?_x-?D₂-A?_1-x random polymer acceptor materials based on NDI?naphthalimide?were synthesized by stille coupling reaction.They are named 0-NDI,0.3-NDI,0.5-NDI,0.7-NDI and 1-NDI?collectively x-NDI?.These five polymers are based on thiophene "D1" units,selenium as "D2" unit,A unit for the NDI.These five polymers were characterized by TGA,GPC,UV-Vis,CV and XRD.The results showed that:the thermal property of polymer x-NDI is better;The solar spectrum has two strong absorption peaks,the absorption limit value reaches the near infrared region;Electrochemical analysis showed that the five polymers matched the donor of PBDT-TPD energy level;XRD analysis showed that the ?-? stacking space of the five polymers was small and the crystallinity was strong.2.In order to find the donor material that matched the five polymer receptor materials x-NDI,we synthesized two types of polymer donor materials.One is the new D-A1-D-A2 conjugated polymer DPP-3T?6?-TPD,and the other two are the traditional D-A polymer PBDT-TPD,PBDTT-FBT.The method of synthesizing polymer DPP-3T?6?-TPD is direct arylation reaction,and the method of synthesizing polymer PBDT-TPD,PBDTT-FBT is stille coupling reaction.The three polymers were characterized by TGA,GPC,UV-Vis and CV.The results showed that:The thermal properties of the three polymer donors are better;the UV absorption of three polymer donors are complementary to the acceptor material x-NDI;Electrochemical analysis showed that the three polymers matched the PC71BM energy level as a donor material for polymer solar cells.However,the driving force of the polymer DPP-3T?6?-TPD was slightly insufficient when matched with the 0.5-NDI level of the acceptor material.3.The best donor material for the preparation of the device with x-NDI receptor material was PBDT-TPD from the donor materials DPP-3T?6?-TPD,PBDT-TPD and PBDTT-FBT.And we selected the better polymer acceptor 0.3-NDI and 0.5NDI with the polymer donor PBDT-TPD for device optimization.The effects of the concentration of the blend solution,the ratio of the blend,the solvent and the additive,and the cathode buffer layer on the photoelectric conversion efficiency of the device were discussed.Finally,the photoelectric conversion efficiency of the polymer x-NDI and donor PBDT-TPD devices was optimized to be 1.80%,4.57%,5.37%,2.05%and 4.70%,respectively.The device performance was then verified using atomic force microscopy?AFM?,external quantum efficiency?EQE?,and electron/hole mobility.The results of external quantum efficiencies show that the responses of these two acceptors to sunlight are complementary and enhance the response to sunlight.These two D/A blends are complementary to response to sunlight and enhance the response.At the same time,an important reason for the high efficiency devices prepared by 0.5-NDI and PBDT-TPD is that the active layer forms a distinct fiber-like network structure with low roughness,which is conducive to the interface between the active layer and the electrode contact,is conducive to the transmission of charge.